A man uses his mobile phone as he stands next to bodies covered in sheets at the site of a blast, outside a public park in Lahore, Pakistan, March 27, 2016. Photo courtesy REUTERS/Mohsin Raza

LAHORE, Pakistan, March 28 (Reuters) – Pakistani authorities on Monday (March 28) hunted members of a Taliban faction which once declared loyalty to Islamic State after the group claimed responsibility for an Easter suicide bomb targeting Christians that killed at least 70 people.

The brutality of Sunday’s attack by Jamaat-ur-Ahrar, the group’s fifth bombing since December, reflects the movement’s attempts to raise its profile among Pakistan’s increasingly fractured Islamist militants.

At least 29 children enjoying an Easter weekend outing were among those killed when the suicide bomber struck in a busy park in the eastern city of Lahore, the power base of Prime Minister Nawaz Sharif. Pakistan is a majority-Muslim state but has a Christian population of more than two million.

It was Pakistan’s deadliest attack since the December 2014 massacre of 134 school children at a military-run academy in the city of Peshawar that prompted a big government crackdown on Islamist militancy.

“Our resolve as a nation and as a government is getting stronger and (the) coward enemy is trying for soft targets,” Sharif said, according to a statement from his office, calling for stronger intelligence coordination.

Jamaat-ur-Ahrar claimed responsibility for the attack late on Sunday night and issued a direct challenge to the government.

“The target was Christians,” a faction spokesman, Ehsanullah Ehsan, said. “We want to send this message to Prime Minister Nawaz Sharif that we have entered Lahore.”

Lahore is the capital of Pakistan’s richest province, Punjab, and is seen as the country’s political and cultural heartland.

Markets, schools and courts in Lahore were closed on Monday as the city mourned.

Rescue services spokeswoman Deeba Shahnaz said at least 29 children, seven women and 34 men were killed and about 340 were wounded, with 25 in serious condition.

Jamaat-ur-Ahrar has claimed responsibility for several big attacks since it split from the main Pakistani Taliban in 2014.

While it mostly focuses attacks in its base of the northwestern Mohmand tribal area, it has previously carried out at least two major attacks in Lahore: one in 2015 that targeted two Christian churches and another at the Wagah border between India and Pakistan in late 2014.

Pakistan has been plagued by militant violence for the last 15 years, since it joined a U.S.-led campaign against Islamist militancy after the Sept. 11, 2001, al Qaeda attacks on the United States.

While the army, police, government and Western interests have been the prime targets of the Pakistani Taliban and their allies, Christians and other religious minorities have also been attacked.

Nearly 80 people were killed in a suicide bomb attack on a church in the northwestern city of Peshawar in 2013.

Security forces have killed and arrested hundreds of suspected militants under the crackdown launched after the 2014 Peshawar school massacre.

Militant violence had eased but the groups retain the ability to launch devastating attacks.

Most militants, like the Pakistani Taliban, are fighting to topple the government and introduce a strict interpretation of Islamic law.

However, the entrance of the separate Islamic State ideology from the Middle East – unlike the Taliban, Islamic State envisions a global caliphate and emphasises killing Christians and minority Shi’a Muslims – has also raised worries it could intensify sectarian violence in Pakistan.

Jamaat-ur-Ahrar in September 2014 swore allegiance to Islamic State, also known as Daesh.

“We respect them. If they ask us for help, we will look into it and decide,” spokesman Ehsan told Reuters of Islamic State, while rejecting the main Pakistani Taliban leadership.

By March 2015, however, the group was again swearing fealty to the main Taliban umbrella leadership. The reason for its return to the fold remains murky.

In the Pakistani capital of Islamabad earlier on Sunday, hundreds of hard-line Muslim activists clashed with police in a protest over the execution of a man they consider a hero for assassinating a governor over his criticism of harsh blasphemy laws.

Bodyguard Mumtaz Qadri shot dead Punjab governor Salman Taseer in 2011. Taseer, a prominent liberal politician, had spoken in support of a Christian woman sentenced to death under the law that mandates capital punishment for insulting Islam or the Prophet Mohammad. Qadri was executed last month.

There was no indication of a connection between the protest in Islamabad and the bomb in Lahore.

However, in March, Jamaat-ur-Ahrar spokesman Ehsan said another attack by the group – a suicide bombing that killed 10 at a court near Mohmand – was “especially done as vengeance for the hanging of Mumtaz Qadri”.

(Reporting by Asad Hashim; Writing by Robert Birsel and Kay Johnson.; Editing by Nick Macfie)